Correct sense of "aspect"

Solution 1:

The second definition of aspect is appropriate here. The context in which you are using the word is physical, specifically, human anatomy. It is not conceptual, as in the first definition.

Here are two examples of aspect used in context. The first is about posterolateral injury patterns, last sentence of the abstract:

The wide array of injuries to many individual anatomic components that we found indicates the complexity of injuries to the posterolateral aspect of the knee.

This is a slightly older example, The structure of the posterolateral aspect of the knee. It is frequently cited. The abstract is brief, but makes clear that aspect is not used as point of view, but as a description of a physical direction.

Solution 2:

Sense 2.

Translated into the vernacular, "The shoulderblade is the back part of the shoulder girdle. In humans, it's a flat triangular bone set on one side of the back of the ribcage."